324 BIRD BEHAVIOUR 



the colour of these does not change, and that 

 the neck-skin is but slightly relaxed, though the 

 beak-caruncle elongates, and there arises an almost 

 conical comb, crowned with warts, on the top of 

 the head. In the Green Jungle-cock the single 

 wattle is let down, and the face becomes red, on 

 excitement. 



In the Common and Silver Pheasants the bare 

 skin of the face expands both above and below 

 when excitement supervenes, and the same pheno- 

 menon is seen in others, such as the blue-faced 

 Firebacks (Lophura), but there is here no colour- 

 change. On the other hand, colour-change may 

 occur without change of form of the naked parts ; 

 thus in the Caracara Hawk when courting, and 

 sometimes under other circumstances, the salmon- 

 pink cere and bare face become pale yellow ; and 

 the red face of the Bateleur Eagle (Helo tarsus 

 ecaudatus) becomes yellow, and its red feet flesh- 

 coloured, when feeding, the change beginning even 

 at the sight of food. Yet when showing off, which 

 this species, unlike other birds of prey, constantly 

 does, the face and feet become intensified in their 

 red colour. 



In the Pileated Vulture (Neophron pileatus), on 

 the other hand, the sight of food makes the livid 

 bare parts of the head turn brilliant rose-pink. In 

 the Blue-and-yellow Macaw (Ara ararauna) and the 

 Cape Crowned Crane (Balearic a cbrysofelargus) the 

 chalky white bare face blushes % reddish on excite- 

 ment. Thus we may see among birds a facial 



